The present invention relates to a heavy duty tire, more particularly to a heavy duty tire having sidewalls improved to reduce the tire rolling resistance without impairing the durability.
In recent years, vehicle fuel cost reduction has been strongly demanded in connection with global environment problem, so various attempts for reducing the rolling resistance of tires have been made. Reduction of the rolling resistance is particularly effective for heavy duty tires used for vehicles such as trucks and buses, since the fuel consumption thereof is large.
For reducing the rolling resistance of heavy duty tires, it has been conventionally attempted, for example, to use a rubber material is having a low energy loss in a tread of the tires, or to decrease a strain generated when the tires are deformed under loading. However, the former method has a fear that the steering stability and the wear resistance are deteriorated. In case of the latter method, ride comfort is apt to lower. Like this, conventional methods still stand improvement.
On the other hand, JP-A-2002-127718 discloses a pneumatic tire capable of preventing crack generation in a sidewall portion wherein a sidewall rubber composed of an axially inner rubber layer and an axially outer rubber layer is disposed in the sidewall portion. However, there is no teaching about reduction of rolling resistance.
It is an object of the present invention to provide a heavy duty tire capable of reducing the rolling resistance without impairing the durability of the sidewall portion.
This and other objects of the present invention will become apparent from the description hereinafter.